audio-talk

Yes....... but at the same time as we do
I need a shed to bugger off into. Might save my sanity

Got the cole fixed again, not by me, sent it up to mi dads for him to have a look at it

Apparently it was one of the ccs devices on the anodes of the valves that had packed up, so the output valve on one channel was practically in cut-off

It will stay up at mi dads for a bit, might spur him on to build a valve phono stage now he's adamant the 45 amp wont be faffed about with

Btw, does anyone know what the ccs should be set at? I found the circuit schematic but it doesnt have any values for the voltages and currents other than the psu output voltage

I found a diagram in google images.
The valves appear to operate at 65V according to that picture off the DIYHS site. I set them all at that voltage first, then set the currents to match each other by using the 1K resistors to read the drops directly as mA. I took an average of both sides of each ECC88, when working at 65V, then set the currents to that average value. It really didn’t need that much tweaking to zero them in.

I don’t have any IXP10M45S devices, so just used a DN2540N5 (got plenty of those) for the repair instead. The objective was TV repairman pragmatic, ie to get it going. Doesn’t matter how much the thing cost or how exotic the S&B LCR units, if it don’t work it’s worthless. Sounds perfectly good to me. In fact, it’s lovely, natural, just rolls along and goes beautifully with the sound of my 45 amplifier.

I was looking for something to build. Obviously I can’t afford expensive LCR units, but a phono stage is looking increasingly attractive as the next project. This Cole thing makes my vinyl sound better than my digital, so hopefully a more conventional valve phono stage might do a similar job (he said with fingers crossed and a ton of hope.)

This phono stage seems to be well regarded and reasonably economical Steve;

https://www.diyaudio.com/forums/analogu ... phono.html

If it's of interest I can donate a Maida reg board and a couple of generic LM317 type boards.

IIRC there's a gerber file available somewhere in the thread to get some PCBs made up.

Ray P wrote: ↑Tue Aug 10, 2021 7:18 pm This phono stage seems to be well regarded and reasonably economical Steve;

https://www.diyaudio.com/forums/analogu ... phono.html

If it's of interest I can donate a Maida reg board and a couple of generic LM317 type boards.

IIRC there's a gerber file available somewhere in the thread to get some PCBs made up.

Interesting. Cheers Ray. I'll peruse that thread

Ugh !
1.4ma driving a 22k RIAA network ... ?
and only 4ma for the output ?

IslandPink wrote: ↑Tue Aug 10, 2021 7:57 pm Ugh !
1.4ma driving a 22k RIAA network ... ?
and only 4ma for the output ?

Indeed. Also, that 0v bias input valve, I assume someone thinks that it's still going to have a high input impedance when it comes to the load the cartridge sees?

Think about what your budget for shelf space and transformer power would be, Steve.
Mine covers about 52 x 30cm. It has a 300V B+ with 72ma total for the signal circuit including a 20ma shunt.
Then there's filaments obviously , 4x D3a and a 5R4.
D3a's are getting too expensive but there are various cheaper options.

IslandPink wrote: ↑Tue Aug 10, 2021 7:57 pm Ugh !
1.4ma driving a 22k RIAA network ... ?
and only 4ma for the output ?

As I said, it seems well regarded and economical...

By whom ? When I go on DIY Audio, I often find myself thinking 'In the land of the blind, the one-eyed man is king'.

In agreement with everything Mark and Nick have said so far.
In some ways, that's not very helpful.

First stage should be high gain. SL7, AX7, cascode, wimpy pentode or variation of these will need to feed a hi Z eq.

Hi gm triode/pentode can drive much lower Z eq. My preference. Can be tricky to get right.

Go for proper biasing imo.

Choose 2nd stage for gain needed and output Z requirement.

The Cole probably sets quite a high bar.

IslandPink wrote: ↑Tue Aug 10, 2021 9:34 pm By whom ? When I go on DIY Audio, I often find myself thinking 'In the land of the blind, the one-eyed man is king'.

I have no interest in vinyl replay so have no horse in this race and I'm simply reporting what I have read - Salas is a well respected designer and builders of his circuit have been positive about their listening experiences, which I have no basis to discard. Steve seems to be looking for an affordable phono project that he can build and enjoy listening to music through, not something that will consume his resources and sitting room - I just offered a possible candidate but I'm sure there are many more. He ho!

Interestingly much later there's another version that has higher Z eq that he likes much better.

Also much much later he talks about biasing the first stage with a diode.

And using a 6SL7. There's much to like about it. The Russian version could be good too though I don't know the valve he uses.